Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$89.26	3.332%	$92.2341	$92.23	$92.25	$92.20
Purchase #2	$31.32	4.229%	$32.6445	$32.64	$32.65	$32.60
Purchase #3	$50.36	3.422%	$52.0833	$52.08	$52.10	$52.10
Purchase #4	$162.43	6.230%	$172.5494	$172.55	$172.55	$172.50
Purchase #5	$187.97	12.625%	$211.7012	$211.70	$211.70	$211.70
Purchase #6	$67.96	3.825%	$70.5595	$70.56	$70.55	$70.60
Purchase #7	$124.45	3.476%	$128.7759	$128.78	$128.80	$128.80
7 purchase totals =	$713.75		$760.5479	$760.54	$760.60	$760.50